Micromechanical approach to unsaturated water flow in structured geomaterials by two-scale computations

This article presents a micromechanical approach to the problem of unsaturated water flow in heterogeneous porous media in transient conditions. The numerical formulation is based on the two-scale model obtained previously by periodic homogenization. It allows for a coupled solution of the non-linear flow equations at macroscopic and microscopic scales and takes into account the macroscopic anisotropy of the medium and the local non-equilibrium of the capillary pressure. The model was applied to simulate two-dimensional water infiltration at constant flux into an initially dry medium containing inclusions of square and rectangular shapes. The numerical results showed the influence of the inclusion–matrix conductivity ratio and the local geometry on the macroscopic behavior. The influence of the conductivity ratio manifested itself by the acceleration or retardation of the onset of the macroscopic water flux at the outlet, while the local geometry (anisotropy) significantly affected the macroscopic spatial distribution of the water flux. Such type of approach can be extended to simulate coupled phenomena (for example hydro-mechanical problems) with evolving local geometry.     

煤矿区构造环境内涵及类型划分

开展煤矿区构造环境类型划分是提高采煤沉陷预计精度的有效途径。将影响采煤沉陷地质因素总结为构造介质、构造界面、构造形态和构造应力4个因素,在此基础上探讨了煤矿区构造环境的内涵,确定了煤矿区构造环境类型分类的指标。认为煤矿区构造环境突出采煤沉陷灾害发生的地质构造背景是地质环境的重要组成部分,更多地反映着地球的内动力地质作用。按照构造介质的不同,把煤矿区构造环境划分为浅埋介质型和深埋介质型;按照构造界面的不同,将其分为连续型、似连续型和不连续型;按照构造形态的不同,将其划分为近水平型、倾斜型和褶皱型;按照煤矿区构造应力的性质,把煤矿区构造环境划分为自重应力型、挤压构造型和拉张构造型。以铜川矿区为例,对煤矿区构造环境类型做了划分,铜川矿区以A型构造环境为主。      

A linear constitutive model for unsaturated poroelasticity by micromechanical analysis

This paper extends the Biot theory of poroelasticity from the saturated to unsaturated case. The Biot phenomenological model uses parameters that are easily observable, such as the deformation of porous frame, total stress, pore pressure, and fluid specific discharge. Such model is preferred for engineering applications. At this macroscopic level, the extension of Biot theory from saturated to unsaturated is straightforward. The constitutive constants, however, are combined properties of solid, pore space, and fluids. In the unsaturated case, the constants are functions of the degree of saturation. Their measurements and tabulation over a range of saturation is generally not feasible for practical applications. In this work, a Biot-Willis type analysis is performed for the unsaturated case to provide a theory that the bulk material constants can be evaluated using laboratory measurable micromechanical constants under saturated condition, plus a capillary pressure curve (saturation versus suction pressure) typically available for unsaturated porous medium, without the need of measurement at each state of saturation. In particular, it is demonstrated that the surface energy contained in the meniscus interface manifests as a “capillary modulus,” given by the negative inverse slope of the capillary pressure curve. A rigorous analysis based on the thermodynamic variational energy approach is also conducted to lend theoretical support to the phenomenological approach. The presented model can bring a closure to the practical engineering modeling of the deformation of partially saturated porous medium that lacks the information of material constants over the range of saturation.     

兰坪盆地古近系宝相寺组层序地层分析

文章运用层序地层学原理,对兰坪盆地中部古近系宝相寺组进行深入研究,划分出1个Ⅰ型层序及3个Ⅱ型层序界面。阐述了兰坪盆地中部古近系宝相寺组层序格架及砂体结构特征,建立层序地层格架演化模式图,反映了湖平面变化对砂体沉积结构的重要影响。低位体系域早期河流侵蚀强烈,多以中粒为主,晚期发育复合状砂体;湖侵体系域砂体多为细粒砂泥岩,呈孤立状形态;高位体系域砂体以席状砂体为主,主要由滨浅湖、半深湖和湖泊三角洲沉积体系构成。     

Response of an anisotropic liquid-saturated porous medium due to two dimensional sources

Eigenvalue approach, following Laplace and Fourier transforms, has been employed to find the general solution to the field equations in an anisotropic liquid-saturated porous medium, in the transformed domain. The results of isotropic liquid-saturated porous medium can be derived as a special case. A numerical inversion technique has been applied to get the solutions in the physical domain. To illustrate the utility of the approach, an application of infinite space with impulsive force at the origin has been considered. The results in the form of displacement and stress components have been obtained and discussed graphically for a particular model.     

云南普朗斑岩型铜矿床成矿流体特征及矿床成因

普朗铜矿床为滇西北地区一超大型斑岩型铜多金属矿床,它产于印支晚期石英闪长玢岩-石英二长斑岩-花岗闪长斑岩复式侵入体内,已有研究表明其形成于印支期。本次流体包裹体岩相学、显微测温及碳、氢、氧同位素综合研究表明:黄铜矿±黄铁矿-石英脉石英中主要发育含NaCl子矿物三相、气液两相及富气相3种类型的包裹体,成矿流体属中高温、高盐度(w(NaCl))NaCl-H₂O热液体系,来源于印支晚期岩浆活动;辉钼矿±黄铜矿-石英脉石英中发育含NaCl子矿物三相、气液两相及含CO₂ 3种类型的包裹体,成矿流体属中高温、高盐度NaCl-CO₂-H₂O热液体系,推测来源于后期岩浆活动;晚期黄铜矿±辉钼矿-方解石脉中主要发育气液两相包裹体,成矿流体为中低温、低盐度NaCl-H₂O热液体系,系NaCl-CO₂-H₂O型成矿流体演化产物。据此,结合区域广泛叠加发育燕山期斑岩钼矿化成矿背景,提出普朗超大型斑岩矿床可能存在燕山期Mo、Cu成矿作用叠加的认识。     

安徽省大别山东段江岭地区榴辉岩及其围岩的变质作用研究

安徽省大别山东段江岭地区的南大别碰撞杂岩主要由榴辉岩、云母片岩－变粒岩及片麻岩系组成,这三套岩石具有不同的变质演化阶段和Ｐ－Ｔ轨迹：榴辉岩有５个变质阶段,早期出现超高压型、高压型、晚期为中压型;云母片岩－变粒岩有４个变质阶段,早期出现高压型,晚期为中压型;片麻岩系仅有一期中压绿帘角闪岩相变质。三套岩石变质历史的差异,反映其所经历的构造过程不同,三者在构造作用下混杂到一起,构成碰撞混杂岩。     

Dimensionless straight line fitting method for hydrogeological parameter determination

Aquifers may have alluvium deposits, weathered layers, fractured zones, and karstic formations separately or in mixture forms. Such geological configurations do not allow classical aquifer test applicability, due to a set of underlying assumptions that are not usually valid in nature. In practice, the Jacob straight line method is the most commonly used approach for aquifer parameter determinations. Constant transmissivity and storativity estimations depend on large time-drawdown plots on semilogarithmic paper as a straight line. A common mistake is that the appearance of a general trend as a straight line on semilogarithmic paper is taken as guaranteed for the application of Jacob method. Since Jacob straight line is the large time extension of Theis type curve, there is only one straight line on the semilogarithmic paper that can represent Jacob method, which is based on the assumption that the aquifer is porous and homogeneous. In such a case, the Jacob method slope should equal to 2.3, which shows its validity. Otherwise, a modification of Jacob method is suggested in this paper. The basis of the methodology is a dimensionless type straight line approach for the aquifer parameter assessment. Its application is presented for aquifer test data from Oude Korendjik porous medium aquifer data. The application results indicate that the classical Jacob straight line method might not be valid without a preliminary check. The dimensionless reevaluation of existing data helps to check the validity. The necessary formulations for the modification of the classical straight line method are derived, which reduce to classical Jacob method for a specific set of parameters.     

滇西北红山铜矿床成矿流体地球化学特征及矿床成因

红山铜矿床为滇西北地区一大型斑岩-矽卡岩型铜多金属矿床,它产于印支期石英闪长玢岩及燕山期石英二长斑岩体内及其周边地层中,其形成经历了多期次热液叠加成矿作用过程.流体包裹体岩相学、显微测温及碳、氢、氧稳定同位素综合研究表明,矿区早期成矿流体为中高温、高盐度NaCl-H2O体系热液,主要来源于印支晚期岛弧型岩浆活动,对区内矽卡岩型矿化形成起了重要作用;晚期成矿流体为中高温、高盐度NaCl-CO2-H2O体系热液,主要来源于隐伏的燕山期后造山伸展型花岗质岩浆侵入体,形成了区内斑岩型Cu、Mo及相关的Pb、Zn多金属矿化.因此,红山铜矿床是两期岩浆热液叠加成矿作用结果.     

Wave propagation in a general anisotropic poroelastic medium: Biot’s theories and homogenisation theory

Anisotropic wave propagation is studied in a fluid-saturated porous medium, using two different approaches. One is the dynamic approach of Biot’s theories. The other approach known as homogenisation theory, is based on the averaging process to derive macroscopic equations from the microscopic equations of motion. The medium considered is a general anisotropic poroelastic (APE) solid with a viscous fluid saturating its pores of anisotropic permeability. The wave propagation phenomenon in a saturated porous medium is explained through two relations. One defines modified Christoffel equations for the propagation of plane harmonic waves in the medium. The other defines a matrix to relate the relative displacement of fluid particles to the displacement of solid particles. The modified Christoffel equations are solved further to get a quartic equation whose roots represent complex velocities of the four attenuating quasi-waves in the medium. These complex velocities define the phase velocities of propagation and quality factors for attenuation of all the quasi-waves propagating along a given phase direction in three-dimensional space. The derivations in the mathematical models from different theories are compared in order to work out the equivalence between them. The variations of phase velocities and attenuation factors with the direction of phase propagation are computed, for a realistic numerical model. Differences between the velocities and attenuations of quasi-waves from the two approaches are exhibited numerically.     

Geochemical features of the ore-bearing medium in uranium deposits in the Khiagda ore field

The Neogene uranium deposits of the Khiagda ore field (KOF) belong to the paleovalley variety of the hydrogene type and differ from other deposits of this genetic type in the geological and geochemical localization conditions. The contemporary hydrogeochemical setting and microbiological composition of ore-bearing medium are discussed. The redox potential of the medium (Eh is as low as–400 mV) is much lower than those established at other hydrogenic deposits, both ancient Late Mesozoic and young Late Alpine, studied with the same methods in Russia, Uzbekistan, and southern Kazakhstan. The pH of subsurface water (6.86–8.13) differs in significant fluctuations both between neighboring deposits and within individual ore lodes. Hydrogen-forming and denitrifying bacteria are predominant in microbiological populations, whereas sulfate-reducing bacteria are low-active. The consideration of these factors allowed us to describe the mechanism of uranium ore conservation as resulting from the development of the cryolithic zone, which isolates ore lodes from the effect of the external medium. Carbonated water supplied from the basement along fault zones also participates in the formation of the present-day hydrogeochemical setting. Based on the features of the ore-bearing medium, we propose a method of borehole in situ acid leaching to increase the efficiency of mining in the Khiagda ore field.     

Poro-viscoelasticity modelling based on upscaling quasistatic fluid-saturated solids

In this paper, quasistatic models are developed for the slow flow of compressible fluids through porous solids, where the solid exhibits fading memory viscoelasticity. Problems of this type are important in practical geomechanics contexts, for example, in the context of fluid flow through unconsolidated reservoir sands and of wellbore deformation behaviour in gas and oil shale reservoirs, all of which have been studied extensively. For slow viscous fluid flow in the poro-viscoelastic media we are able to neglect the dynamic effects related to inertia forces, as well as the dissipation associated with the viscous flows. This is in contrast to the vast body of work in the poro-elastic context, where much faster flow of the viscous fluids may give rise to memory effects associated with microflows in pores of the solid media. Such problems have been treated extensively in both the dynamic and quasistatic cases. We are taking a specific type of the porous medium subject to slow deformation processes possibly inducing moderate pressure gradients and flow rates characterised by negligible inertia effects. As the result of homogenisation of such a two-phase medium, we observe the fading memory behaviour in the Biot modulus which controls the pressure increase due to skeleton macroscopic deformation and pore fluid content. Although our derivation leads to a result which is consistent with the formal phenomenological approach proposed by Biot (J Appl Phys 23:1482–1498, 1962), we offer the reader more insight into the structure of the poro-viscoelastic constitutive relations obtained; in particular, we can show that the Biot compressibility evolves in time according to the creep function while the skeleton stiffness is driven by the relaxation function.     

陕西山阳庙梁金矿地质特征及流体包裹体研究

庙梁金矿床位于南秦岭柞水-山阳矿集区的中心地带,为了查明庙梁金矿成矿流体特征、金的沉淀机制及矿床成因,对该矿床不同成矿阶段脉石矿物中的流体包裹体进行了详细的岩相学、显微测温、激光拉曼光谱分析研究并与周边典型金矿床特征进行了对比.结果 表明,该矿床包裹体类型丰富,成矿早阶段主要为H2O-NaCl型包裹体(Ⅱ型)、部分H2...     

Discrete fracture model for simulating waterflooding processes under fracturing conditions

In our study, we develop a model for simulating fracturing processes in a poroelastic medium. The proposed approach combines the discrete fracture model enriched with contact plane mechanics. The model captures mechanical interactions of fractures and a deformable medium, fluid, and heat transfer in fractures and in a porous medium. Both effects of poroelasticity and thermoelasticity are accounted in our model. Mass and heat conservation equations are approximated by the finite volume method, and mechanical equilibrium equations are discretized by means of the Galerkin finite element approach. Two‐dimensional grid facets between 3‐dimensional finite elements are considered as possible fracture surfaces. Most of these facets are inactive from the beginning and are activated throughout the simulation. A fracture propagation criterion, based on Irwin's approach, is verified on each nonlinear iteration. When the criterion is satisfied, additional contact elements are added into finite element and discrete fracture model formulations respectively. The proposed approach allows modeling of existing natural and artificially created fractures within one framework. The model is tested on single‐ and multiple‐phase fluid flow examples for both isothermal and thermal conditions and verified against existing semianalytical solutions. The applicability of the approach is demonstrated on an example of practical interests where a sector model of an oil reservoir is simulated with different injection and production regimes.     

山东张宝庄铁矿水文地质特征研究

张宝庄铁矿矿床位于当地侵蚀基准面以下,呈似层状,倾角多在45°以上,埋深20～888m。对矿区3个主要含水层及其之间的水力联系进行分析,这3个含水层分别为第四纪全新世冲洪积孔隙水含水层、基岩风化裂隙水含水层和泰山岩群变质岩构造裂隙水含水层,各含水层之间水力联系较弱。另外还研究了矿床充水因素、预测矿床正常涌水量和最大涌水量,在此基础上划分该矿区水文地质条件为中等类型。     

块状岩溶承压含水层非稳定流数学模型的建立及应用

块状岩溶介质可视为双重孔隙介质, 其含水层为承压含水层, 水文地质模型概化为各向同性非均质。根据块状岩溶承压含水层地下水运动规律, 建立二维承压含水层非稳定流数学模型, 采用有限体积法对其求解, 并以深圳葵涌区为例对模型进行识别和验证。结果表明: 各时段的计算水位值与实测水位值非常接近, 所建立的数学模型正确可应用。     

污染检测试井新图版及其应用

本研究提出了考虑续流和污染类似于麦金利图版的新图版。这种新图版既适用于压降试井,又适用于压力恢复试井;既适用于具有高传导的垂直裂缝试井,又适用于致密低渗透储层试井分析;既适用于单一介质,又适用于双重介质。     

Buckling of layered elastic media: A cosserat-continuum approach and its validation

In this paper the stability of layered, anisotropic, hypoelastic media under initial stress is investigated. The bifurcation problem is formulated and solved numerically by use of a semi-analytical transfer matrix method. An alternative analytical approach in dealing with inhomogeneous media is developed by representing a periodically layered medium as a homogeneous Cosserat continuum. The Cosserat-continuum approach is validated against the numerical transfer matrix solution.     

岩土破损力学的系统论基础

天然岩土材料与其它材料的根本不同点在于它的结构性,而形成结构性的根本原因在于胶结的不均匀性.胶结强的部位形成结构体,胶结弱的部位形成结构面.岩土材料是由结构体和破损带组成的二元介质.本文分析了岩土材料的系统特性,对岩土破损力学进行了介绍,从非线性科学的角度阐述了岩土破损力学的系统论基础.     

大兴安岭北段旁开门金(银)矿床地球化学特征及成因

旁开门金(银)矿床地处爱辉—呼玛成矿带,矿床主体赋存于侏罗系甘河组火山岩中,矿体主要以脉状形式产出,严格受硅化角砾岩带控制。区内甘河组玄武安山岩、安山岩、流纹岩属过铝高钾钙碱性系列,玄武岩和石英斑岩属过铝质钾玄系列,它们均来源于地幔岩浆,为同源岩浆分异的产物。矿石中流体包裹体发育较差,以气液两相包裹体为主,仅见少量含子矿物三相包裹体。气液两相包裹体均一温度为268.8～331.6℃,盐度(w(NaCl))为8.67%～13.11%,含子矿物三相包裹体均一温度为288.8～313.3℃,盐度为37.32%～39.23%;表明成矿流体为中温、中—高盐度的热液体系。根据流体包裹体氢、氧同位素分析结果推断其为岩浆流体与大气降水混合热液。矿床形成于早白垩世由挤压转变为伸展环境,成矿物质来源于深部岩浆及火山岩地层,成矿温度为中温,成矿深度属浅成,其成因类型为浅成中温热液矿床。